The invention relates to a system for reducing the biochemical oxygen demand and suspended solids levels in an impure water volume and, specifically, to such a system which employ bark fibers.
Many sources of impure water require treatment to meet the increasingly strict requirements of various government agencies. By way of example, managed marshlands have been employed for further treatment of municipal or industrial waste waters. Such systems benefit wild life and man while minimizing potentially destructive vectors. One problem in such systems is the rapid increases in plant growth brought about by excessive nutrient deposition (eutrophication) in small bodies of water or peripheral portions of large bodies of water, through run-off of soil fertilizers and discharge of such municipal or industrial waste waters, can result in "blooms" of aquatic algae and a rapid disruption of the normal trophic balance between algae and algal feeders. Such increases in algae do not pass normally into the food chain as most fish and some lower forms of animal life cannot feed on algae. When such water supplies are designated for human consumption, excessive amounts of algae can produce disagreeable odors and "fishy" tastes as well as clogging of filtration machinery.
A particularly effective ecological system for controlling such marshlands is described in my U.S. Pat. No. 4,086,161. Briefly summarized, the system makes use of clusters of substantially individualized bark fibers positioned in the upper relatively oxygen-rich zones of the water body which attract and hold excessive nutrient deposits in the form of colloidal wastes and aquatic algae produced by the same while providing a safe habitat for algae predators in the form of minute animal organisms. The bark fiber clusters serve to prevent disruption in the trophic balance.
While the aforementioned marsh system is highly effective as an ecological system, when liquid is withdrawn from the body of water, it may include zooplankton and invertebrates which could exceed the requirements of such government agencies as the Environmental Protection Agency and various state water quality control boards. In addition, such organisms could cause plugging problems if the effluent were to be further processed through ion exchange or reverse osmosis methods, as for drinking water use.
Thus, it is desirable to provide a treatment system particularly adapted for the further treatment of impure water from a source such as the aforementioned controlled water bodies to reduce its biochemical oxygen demand and suspended solids level and eutrophic chemicals such as nitrogen, phosphorous and dissolved carbon dioxide.